The present invention relates to a specified polyimide powder useful for the materials of high-temperature stable adhesives, coats, molded parts and composites.
Many kinds of industrial materials which are further excellent in high-temperature properties, are required for high performance and weight saving in the field of electronics, aeronautics and space instruments, and transport machinery. Polyimides are known as improved materials suitable for these applications and are used for structural adhesive, molding materials and composites.
Conventional polyimides, however, are difficult for use, because melt flowability becomes very low in the stage of containing polyimide as a major component after almost cyclization, although the polyamic-acid precursor is flowable when melted.
The melt flowability increases in the presence of solvents or polyamic-acids. Evaperation of the residual solvents or the moisture generated by the cyclization of amic-acid groups, however, causes voids and property reduction, when the solvent removal and imidization is performed in the following step.
National Aeronautics and Space Administration (NASA) has developed new polyimides having improved melt flowability by heat imidizing polyamic-acids which are obtained by reacting tetracarboxylic acid dianhydrides such as 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride, pyromellitic dianhydride etc., with diamines such as 3,3'-diaminobenzophenone etc. in organic solvents (for example, U.S. Pat. No. 4,065,345 U.S. Pat. No. 4,094,862), and variety of their applications are reported in SAMPE Quarterly, p.20-25(October 1981).
The object of this invention is to provide the polyimides and a method for preparing the same which are further improved in melt flowability and can be widely used for the high-temperature stable adhesives and/or coatings. Another object of this invention is to provide a method for adhesion and coat forming of the polyimides.
Still another object of this invention is to apply said technology and to provide a method for preparing prepreg, bonding by use of said prepreg, and preparing molded laminates of said prepreg.